A metal thin film resistor is very thin, and thus, when a contact hole is formed directly on the metal thin film resistor, the contact hole may penetrate through the metal thin film resistor to connect the metal thin film resistor to a wiring positioned below the metal thin film resistor.
Conventionally, to prevent a metal thin film resistor from being connected to a wiring positioned below the metal thin film resistor, the following semiconductor device has been known. To be specific, this conventional semiconductor device includes a metal thin film resistor formed on an inter-layer insulating film, two conductive etching stopper films having conductivity and formed to be spaced apart from one another on a surface of the metal thin film resistor, an insulating layer formed on the inter-layer insulating film to cover the metal thin film resistor and the etching stopper films, and two contact holes extending from a surface of the insulating film to the etching stopper films, respectively. In such a conventional semiconductor device, since the conductive etching stopper films are formed on the metal thin film resistor, the contact holes can be prevented from penetrating the metal thin film resistor. Accordingly, the metal thin film resistor can be prevented from connecting to a wiring positioned below the metal thin film resistor.
The above conventional semiconductor device can be manufactured, for example, as follows. Initially, a thin film resistor layer of a material for a metal thin film resistor is formed on an inter-layer insulating film. A first insulating film is then formed on the thin film resistor layer. Subsequently, two thin contact holes are formed to be spaced apart from one another in the first insulating film, extending from a surface of the first insulating film onto a surface of the thin film resistor layer. Thereafter, a conductor layer of a material for etching stopper films is formed on the surfaces of the thin film resistor layer and the first insulating film. Accordingly, the conductor layer connected to the thin film resistor layer is buried in the two thin contact holes. Then, the thin film resistor layer, the first insulating film, and the conductor layer are etched to be patterned such that the thin film resistor layer remains only in a required location. Thereafter, the conductor layer on the thin film resistance layer (i.e., metal thin film resistor) is divided into two parts through the etching such that it includes conductor layers buried in the different thin contact holes, respectively. Accordingly, two etching stopper films are formed in positions spaced apart from one another on the surface of the metal thin film resistor. Thereafter, a second insulating film is formed on the inter-layer insulating film to cover the surfaces of the metal thin film resistor, the first insulating film, and the conductor layer. And then, two deep contact holes extending from the surface of the second insulating film onto each of the etching stopper films are formed in the second insulating film.
This manufacturing method, however, takes time because of the large number of processes. Further, masks are required in four processes of forming the thin contact holes, etching the thin film resistor layer, separating the conductor layer into two parts, and forming the deep contact holes, which results in an increase in cost for manufacturing the masks.